Study On The Hydroesterification Of (P-isobutyl)Styrene Catalyzed By Metal Carbonyls

Ibuprofen, an important non-steroidal anti-inflammatory drug, has become one ofthe largest inflammation antipyretic analgesics. Many synthetic methods for ibuprofenhave been developed. BHC synthesis process is a new method because of its higheratom economy and lower pollution. But the recovery and recycling of noble metalcatalysts are difficult.In this paper, the hydroesterification of styrene and its derivatives catalyzed by thetransition metal （Co, Pd） complex was studied and a possible catalytic reaction mechanismwas proposed. The functionalized carbonyl cobalt ionic liquid catalyst was prepared by ametathesis reaction and was used as catalyst for the hydroesterification of IBS, inwhich the recovery of catalyst could be realized.Firstly, the hydroesterification of styrene catalyzed by Co₂（CO）₈was studied andthe possible catalytic reaction mechanism was proposed according to the experimental results. Theresults indicated that the conversion of styrene approached100%and the yield ofmethyl α-phenylpropionate reached89.07%, meanwhile i/n=24.352under thefollowing reaction conditions: toluene as solvent, n（Co₂（CO）₈）/n（styrene）=0.06, pyridi-ne as promoter and n（pyridine）/n（Co）=2, CO pressure6.0MPa, reaction temperature95℃for12h.It was confirmed that hydroesterification of IBS using PdCl₂/PPh₃/CuCl₂ascatalyst gave high catalytic activity and selectivity to the formation of branched esterin the ionic liquid solvent. The optimum conditions were obtained as followed:[Bmim]BF₄ionic liquid as solvent, reaction temperature80℃, CO pressure6.0MPa,the reaction time24h. Products could be extracted from ionic liquid by n-heptane, inwhich the recovery of catalyst could be realized. But the conversion of IBS wasreduced to36.68％, the selectivity of branched ester was invariant when the secondusing. The functionalized ionic liquid catalyst [Bmim][Co（CO）₄] was prepared by ametathesis reaction between [Bmim]Cl and KCo（CO）₄, which structure wascharacterized by FT-IR and was applied in the hydroesterification of IBS. Although theconversion of IBS only reached40.36％, the selectivity of branched ester approached100%. And the reactant and product could be extracted from ionic liquid by n-heptane,in which the recovery of catalyst could be realized.